1. Field of the Invention
The apparatus and method of the present invention relates to chemical cutters. More particularly, the present invention relates to a method for inserting an aluminum sleeve along the body of a metal or steel riser in order to protect the steel riser from cutting or damage should a chemical cutter inadvertently fire while positioned within the wellhead assembly.
2. General Background
During the drilling and production of oil wells, but more particularly during that portion of the drilling activity which involves the recovery of pipe from the borehole, the pipe is usually retrieved in sections out of the borehole. In order to retrieve sections of pipe, the pipe must be spliced or cut while down the borehole, so that the uppermost section can be retrieved from the remainder of the pipe in the well. One such method of cutting the pipe is to utilize a cutting system known as chemical cutters, which are usually a firing mechanism positioned at the end of a wireline, the firing mechanism including a plurality of ports within the lower end of the firing mechanism, so that when the mechanism is fired, a stream of chemical compound is blown from the cutter head, and, in effect, eats or cuts its way through the pipe within the borehole. In most instances, the type of pipe which is utilized is a steel pipe, which is quite reactive with the chemical compound within the cutter, so that upon contact with the steel pipe, the chemicals will cut through the steel, and therefore, enable the section of pipe above the cut to be retrieved.
One of the hazards in utilizing the chemical cutter, is that the cutter mechanism, as was stated earlier, must be hung from the wireline in the well head assembly. The well head assembly is that portion of the drilling rig which extends above the rig floor, upward. Usually, the assembly includes an extended riser, which is a length of steel pipe inner-connecting portions of the well head assembly, for feeding the wireline therethrough. The well head assembly which includes a lubricator can be pressured up to a certain amount of pressure, while the chemical cutter is positioned therein, prior to it being lowered into the well below the rig floor. The wireline would be threaded through an upper spool on the well head assembly, and threaded through a port, with the chemical cutter attached at the end of the wireline for ultimately being lowered downhole.
One of the hazards which is faced at this point, is the chemical cutter which, although may be set to fire downhole because of the pressure or other reasons, may inadvertently fire when it is housed within the riser between the spool and the floor, and would therefore cut through the wall of the steel riser. This, of course, could be catastrophic in that the well head assembly would, in effect, be severed in two, and the upper portion of the assembly would come tumbling down onto the rig floor, which would certainly cause damage and may cause grave injury or even death to workers in and around the well head assembly. This same inadvertent firing may occur after the chemical cutter has been retrieved from downhole, in the event it failed to fire downhole for some unexplained reason. Often times when that occurs and the chemical cutter is retrieved because the well head assembly may be pressurized or the like, again the chemical cutter may inadvertently fire as it is within the wellhead assembly and the same result will occur.
Therefore, there is presented a need in the industry for devising a method and an apparatus which would protect the wellhead assembly and particularly the wall of the steel riser in which the chemical cutters are housed above the rig floor, so that should there by inadvertent firing of the chemical cutter, that the damage to the riser or well head assembly would be avoided, and a new chemical cutter would simply be positioned in place.